Since the commercial process of producing Nylon-6,6 is in the market since 1939, polyamide resins have become more important than ever in man-made fibers and engineering plastics. The two major raw materials in producing polyamide fiber are caprolactam and adipic acid. The main application of caprolactam is in the production of Nylon-6. Adipic acid is used to make Nylon-6,6. Caprolactam can be obtained by the oximation of cyclohexanone. Adipic acid is made through the oxidation of cyclohexanone. Therefore, cyclohexanone is the major intermediate in the production of caprolactam and adipic acid.
In the industry, there are two major methods for preparing cyclohexanone. One is the dehydrogenation of cyclohexanol to cyclohexanone after the hydrogenation of phenol to cyclohexanol. The other one is the subsequent hydrogenation of benzene to cyclohexane. The cyclohexane is oxidized producing cyclohexanol and a small portion of cyclohexanone. The cyclohexanol is then dehydrogenated to cyclohexanone
The conventional method used in the dehydrogenation of cyclohexanol to cyclohexanone is the direct dehydrogenation reaction as shown in (a): ##STR1## This conventional method has two major disadvantages; (1) unless the temperature is raised, the conversion of cyclohexanol is severely constrained by the thermodynamic equilibrium because the Gibbs free energy is almost zero at the reaction temperature of 227.degree. C.; (2) the reaction is highly endothermic (at 227.degree. C., H=+15.8 kcal/mole), that a high operation cost and expensive shell and tube reactor are needed.
The primary purpose of this invention is to provide an alternative method for the production of cyclohexanone from cyclohexanol without having those two mentioned disadvantages. To achieve this purpose, this invention provides a method of adding a gaseous oxidant in the cyclohexanol feed steam and catalytically converts the cyclohexanol to cyclohexanone. The catalyst used in this invention is the conventional Cu-Zn oxide catalyst. With the addition of this gaseous oxidant in the cyclohexanol feed stream, the reaction heat of the catalytic dehydrogenation of cyclohexanol to cyclohexanone is almost zero. Therefore, an inexpensive insulated reactor can be used in this reaction.